The present invention relates to reciprocating pumps.
In the past, so-called plunger pumps have been mostly so designed that the setting pressure is adjusted by allowing an amount of fluid exceeding the setting pressure to escape to the outside through a pressure regulating valve disposed in a fluid delivery circuit. On the other hand, the displacement is adjusted by such methods as adjusting the amount of eccentricity of the crankshaft, adjusting the number of revolutions of the pump, varying the plunger diameter and so on. However, these prior art methods have the disadvantages of resulting in complicated mechanisms, requiring complex operations, wasting power uselessly, making it difficult to ensure stable delivery or flow rate and so on.